It is known to use propulsion devices of rotating paddle wheel type for boats, e.g. pedalos for recreational use, smaller fishing boats for recreational fishing or other light vessels. To maximize the propulsion efficiency such devices requires that the propulsive paddle wheels are located to at least 50% above water level. If a larger share of the paddle wheel is located below the water level the opposing force, in a direction opposite the direction of movement, will increase. This is partly due to the upper paddles direction of movement but also due to the increased friction in the water. Further, the part of the paddle wheel that is above the water level takes up space in the boat in an already limited space, alternatively obscures the view if the paddle wheels are located on the sides of the boat. This part will further act as an air hole and substantially increase the air resistance of the boat in an environment that is windy and thus decrease the propulsion efficiency. Since this type of propulsion device requires that the paddle wheel size increases if an increased propulsion speed is desirable the above mentioned negative effects will increase further. Boats with paddle wheel propulsion are also sensitive for heavy seas. High waves will lead to that a larger share of the paddles is located above the water level which will further decrease the propulsion efficiency. To increase the usability of these type of boats, there has also been a demand to be able to drive these on land, at least shorter distances such as after discharging from a trailer or parking place to the water, or for working crafts suited for mussel/oyster harvest at breeding places in coastal areas with ebb and tide.
It is known to use wind power plants and paddle wheels with shovels of rotating type for energy production. It is further known to use wave power plants that utilize the upward and downward movements of the waves for extracting energy. The drawback of existing solutions for energy production through wind power plants is that these are so-called fast runners which must be stopped at strong winds in order not to risk failure through loss of the rotor blades. A device with rotating paddle wheels placed in water for energy production must be placed in places such that the shovels are allowed to rotate freely, and such that its impact on the surrounding environment is minimized. The wave power plants ability to extract energy is dependent on the access to relatively high waves, i.e. differences between crests and throughs of the sea.